Waterproof, breathable footwear is typically formed of an upper material which is both air permeable and water permeable. The outer layer of the upper material may be leather and/or a textile fabric. Waterproofness is achieved through the use of a waterproof, water-vapor permeable functional material that is arranged within the shoe. In the footwear art, materials which are both waterproof and water vapor permeable are commonly referred to as “functional” materials. The functional layer may be made of an expanded polytetrafluoroethylene (ePTFE) material available from W. L. Gore and Associates, Inc., Elkton, Md., under the tradename GORE-TEX®. The expanded PTFE is characterized as having a density less than 2.0 g/cm3. Other functional materials, such as polyurethanes, have also been developed and are known in the art.
It is difficult to sew the functional layer directly to the upper and/or sole material of the footwear. In addition, the functional layer becomes permeable to water when it is pierced during the sewing process. It is therefore common to provide the footwear with a shoe insert containing the functional layer. The shoe insert incorporates several pieces of a laminate that includes the functional layer and a textile material which are assembled and joined to produce an insert that includes laminate panels joined by seams in a manner to have generally the shape of a foot. A waterproof joining process may be accomplished by sewing the individual pieces together and sealing the seams with a superimposed adhesive or sealing tape that is applied to the seam by a bonding or welding process.
The shoe insert is generally attached within the footwear such that the upper end of the shoe insert is connected with the upper end of the footwear by sewing or by an adhesive. The sole portion of the shoe insert is held stationary between the outsole and the insole of the footwear, usually by adhesive bonding over the entire surface.
One problem that often results when forming such waterproof, breathable footwear is that the insertion of the shoe insert often results in a poor fitting shoe (i.e., the shoe insert has a different fit (shape or size) to that of the already sized upper) and/or poor attachment between the shoe insert and the shoe upper material, which results, among other things, in a less than desirable appearance of the inside of the footwear (i.e., the shoe insert appears wrinkled or pulls away from the upper).
An additional problem is that because of the multiple laminate pieces or panels needed for manufacturing an article of waterproof footwear, flexibility may be severely compromised. A further problem is that sealing the seamed portions of the shoe insert to make the shoe waterproof may compromise the breathability and flexibility of the shoe and contribute to the poor fit of the shoe insert.
Thus, there remains a need in the art for a shoe insert that closely conforms to the inside of the shoe, is both waterproof and breathable, and is comfortable to wear.